Targeting Th17 cells in autoimmune diseases.

•T helper 17 (Th17) cells have important functions in immunity and pathologic inflammation.•Targeting Th17 cells rather than single effector cytokines may enhance efficacy.•Retinoid-related orphan receptor-γt (RORγt) and interleukin-23 (IL-23) coordinate pathogenic Th17 cell development and function.•Much remains to be learned about how RORγt inverse agonists regulate transcription.•Monoclonal antibodies targeting the IL-23/IL-23R pathway show clinical promise.